Ask Slashdot: Should You Tell Future Employers Your Salary History?

During the interview process for a technology job, I was asked to fill out an application which included questions about my compensation history. When I asked why, I was told that it was part of the background check and wouldn’t be used to determine the size of the offer… What is the risk for the employer of not knowing that info? Is this standard procedure or part of a trend at technology companies?
The original submission asks if this is ever a legitimate question — or more to the point, “Is it anything more than an attempt to gain negotiating leverage?” So leave your best answers in the comments. When you’re interviewing for a new IT job, should you tell future employers your salary history?